class Animal {
    speak() {
        console.log("speak");
        return this;
    }

    static eat() {
        console.log("eat");
        return this;
    }
}

let obj = new Animal();
// Animal {}
obj.speak();
console.log("========")
let speak = obj.speak;
speak(); // undefined

Animal.eat() // class Animal
console.log("========")
let eat = Animal.eat;
eat(); // undefined